Fuel pump relay WTF

[325isdan]

Ok so heres the problem.. my fuel pump relay has been acting up and finaly went.. so put in a new one.. nothing car jsut cranks wont budge.. tryed another relay still nothing.. I can only get the pump to run when i jump the temnials..

anyone know why?

[jlevie]

The pump only runs when the DME sees a timing reference signal as the engine turns over. A lack of the timing reference signal, lack of power to the DME (main relay/fuse), a bad DME, or a wiring problem between the DME and thre fuel pump relay socket can cause the symptoms you've described.

Start by checking the main relay and fuse to make sure the DME is being powered up when the ignition is switched on. If the DME has power replace the timing reference sensor and see if that helps (the only real way to check the sensor is with an occilloscope). If that doesn't cure the problem ohm out the control wire between the relay and the DME. And if all else fails replace the DME.

[325isdan]

if the DME is that other oragne relay i put in a new one to and nothing.. how do i test the DME to make sure its working.do you jumper it?. and what does DME stand for??

thanks..

[325isdan]

if all else fails can i install a switch and manual turn on/off my fuel pump?

[redhatpat]

The DME is the main computer. It's in the glove box.

[325isdan]

how do i check that?

[325isdan]

actually come to think of it.. i did take the computer out of the car.. It was runngin befor that.. I jsut took it out opened it up looked inside to see what kind of chip the car had.. If the chip came unpluged a bit would that keep it from running? how do i test it.

[jlevie]

The only practical test for a bad DME is to swap in a known good unit.

If you fiddled with the chip and didn't get it back in the socket correctly that would prevent the DME from working.

[325isdan]

no i never touched it thats why i dont htink is the DME but who knows.. heres a run down of what happened.

first I drive this car rarley because getting it ready for track use. pretty much bought it and parked it..

The car ran great.. Didnt know that the fuel gauge stoped working at the time and i ran the car out of gas

thought it was the fuel pump. tested everything worked.. found out no gas..
filler her up worked great..

car sat for a bit.

took out the ECU to see what kind of chip was in the car.. bought the car knowing there was a chip but not what kind so i opened it looked inside put it back in the car. touched nothing..

went to start the car . nothing happend jsut cranked.

put in new working relays for the fuel pump and the other orange relay ( main relay?)

nothing

took out the fuel pump relay jumped it and works.

can i put in a fuel pump switch for now so i can atleast run the car? or will that mess it up?

[jlevie]

Pull one spark plug, ground its body to the engine and have someone crank over the car while you watch the plug. If you don't see spark either the DME is the problem or the DME isn't seeing a timing reference signal. Since the last thing you messed with is the DME I'd be inclinded to believe it to be the problem. Make sure that its connector is looks intact, that there arn't any bent pins, and that it is properly seated.

[325isdan]

i get spark and everything just no gas.

[jlevie]

If you have spark the timing reference signal is present and the DME is running. When cranking the engine is fuel relay control signal present?

With the fuel relay jumpered what pressure do you have at the fuel rail?

[325isdan]

thanks.... when you say is the fuel relay control singal present when cranking.. does that mean take a volt reading with the relay in place while cranking the car?

[jlevie]

The relay doesn't have to be in place. What is needed is to know if the coil would be energized when the engine cranks over. Off hand I don't remember if the DME supplies power or ground to the relay. But as a guess I'd say that one of the coil leads gets power and the other lead is grounded by the DME to turn on the relay.

[325isdan]

would harm be done to the car if i jsut install an override switch for the fuel pump and manual turn it on while im cranking the car?.

god damn i hate electrical work.